Only 3lbs of boost when powerbraking?

[bishir]

Today the guys at NAPA wanted to see a burnout by the bad v6 so I powerbraked the car like I do at the track, but this time it would build about 3-4 lbs of boost and not go any higher. I had the gas pushed to the floor too.

Scanmaster settings look normal. My only guess is I might be running to rich on the bottom end, but that is just my guess.

Any other guesses?

James

 

[EMcNeice]

what torque converter and turbo do you have?

 

[bishir]

Oops, forgot! TA-49 and stock converter.

 

[mgmshar]

I have a TA-49, and I had a stock converter. You should be able to get a lot more than 3psi by powerbraking.

Check the stuff that controls boost: exhaust manifolds and cross-over leaks, is wastegate puck stuck open, clogged catalytic converter, blown intercooler hose, etc.

What chip are you running?

 

[bishir]

wastegate puck stuck open

Hmm, you know when I put on the TA-49 I also bought a THDP. With the stock actuator and adjustable rod I had to extend it so far that the puck was actually open some at rest. I'm out of adjustment and the lowest boost I'm running is 20lbs at WOT. Think that is my problem? If, so how do I fix this problem?


James

 

[mgmshar]

I would say "Bingo!"...

With my TA-49 and THDP, I had to really open-up the wastegate hole to get the boost down and keep it controlled (i.e. no creep). I opened up my wastegate hole to about 1-3/16", which is way bigger than what is on the factory housing.

See this link

If you have the rod adjusted so long that the puck is not closed, your turbo will not spool. I tried this (accidentally) when I was diagnosing my creep problem, and having the wastegate puck even a little open killed the turbo.

Good Luck,

 

[bishir]

Mike,

Thanks for the help! Instead of enlarging the wastegate hole could I just go with some kind of boost controller?


James

 

[mgmshar]

If your boost is jumping to 20 psi with the actuator rod just a little tight, then no boost controller is going to help you. The mechanical system is just not capable of keeping the boost down.

Well, now that I think about it, there may be one exception. You could possibly get your chip re-burned to have a much lower wastegate solenoid duty cycle. That may help your problem. Here's how you can find out: take the Y-hose between the turbo, actuator, and solenoid off the car. Connect a new hose from the fitting on the turbo outlet to the actuator. In other words, you're taking the solenoid out of the system. Make sure your connections are tight - you don't want this hose to blow-off during the test (boost will spike up fast if it does - BAD!). Set the actuator rod to the longest it can be while still holding the puck closed. You should have to stretch the rod just a little to get it to slide over the puck. Take the car out and do a WOT run, while watching your boost gauge. The boost you see under this condition is the lowest possible boost your system can get, regardless of what type of controller or chip you use. If the boost is still too high, or if it creeps badly, then you need to port the wastegate hole. If the boost is low and steady, you should be able to get your chip re-burned to control it (after you re-install the Y-hose, of course).

These 49's are a pain. They like to spool so much, they can be difficult to control. It's worth it, though!

 

[bishir]

Thanks again Mike.


I'll try that too. I was just wondering a something like a bleeder valve would help, but I guess not. I really hate to have to pull off the downpipe and turbohousing to do this This all started when I turned down the boost to 20lbs. I was fine running 22lbs of boost, but the boost spikes to 25lbs was hurting me.. Maybe I should run 22lbs and get a boost controller to keep the spikes from happening?

James

 

[Razor]

Are you using the factory "Y" hose and valve cover WG selenoid?

If you have a HD diaphram, then 18 might be the minimum you'll see.

 

[GNVYUS 1]

Stock D5 with my Ta49 only built up 4 lbs of boost on the factory gauge, 3 psi on the aftermarket gauge. This amount of boost if normal on the D5.

You need to open the wastegate hole no doubt. Go no bigger than 1 1/8th and open up the inside. You can do this with a dremel tool and a shop vac (keep out debris)

Then go to a manual boost controller like this
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&category=42604&item=2445356174

With a Ta49, 3000 vigilante,MBC and 17psi, I could chirp the tires on a hammer down at 35 to 40 mph. The boost controller makes a big difference out of the hole and anywhere in the rpm band.

 

[SFITurbo]

James,
Just happen to have a new manual controller "laying around"if you want to try it. I'll even install it if you'll by me that TT WE4 on Ebay for Xmas!

 

[bishir]

tock D5 with my Ta49 only built up 4 lbs of boost on the factory gauge, 3 psi on the aftermarket gauge. This amount of boost if normal on the D5.

When the wastegate puck was closed all the way from the start and I was running higher boost it had no problem boosting all the way on the brake.

Are you using the factory "Y" hose and valve cover WG selenoid?

Yes, would a HD actuator help?

 

[1badTTA]

An HD actuator will limit the lowest boost you will ever see(not what you want) and may already be what you have. You need an HD actuator if you can't raise the boost any more. An example would be if you can only get the boost up to 22psi and want to run 25psi. HTH